The long term objective of this proposal is to understand steroid hormone regulation of peptidergic and aminergic neuronal systems. Immediate aims are to determine the distribution of androgen receptors (AR) in brain, to describe the ontogeny of AR gene expression and determine whether AR colocalizes with other steroid hormone receptors (progesterone, glucocorticoid and estradiol). [3H]Dihydrotestosterone autoradiography will be combined with immunocytochemistry using receptor antibodies that are currently available and well characterized. In addition a modified method of dual immunohistochemistry will be utilized. Biological effects of androgen and other steroid hormones on neuronal functions will be determined by quantitative in situ hybridization assays of messenger RNA for various neuropeptides and neurotransmitter biosynthetic enzymes in peptidergic and aminergic neurons respectively. Initial studies will focus on steroid hormone regulation of neurons producing gonadotropin releasing hormone (GnRH), thyrotropin releasing hormone (TRH), growth hormone releasing factor (GRF) and tyrosine hydroxylase (TH). Using the same method, the effects of androgens and other steroid hormones on AR mRNA levels will be determined. Both testosterone and its nonaromatizable metabolite, dihydrotestosterone, will be administered to distinguish between the effects of androgen and estrogen. Emphasis will be on neurons in which multiple steroid hormone receptors colocalize in order to determine the interrelationships among various steroid hormone actions. Immunohistochemistry will be utilized in an investigation of the mechanism of nuclear translocation of AR using a series of recombinant androgen receptor deletion mutants expressed in COS cells and natural mutants in human genital skin fibroblasts from humans with the androgen insensitivity syndrome. Structural alterations of AR that influence nuclear localization will be correlated with changes in the transcriptional activation function of AR. It is anticipated that these studies will contribute to our understanding of steroid hormone actions in the regulation of brain function.